The present invention relates to a semiconductor device and a process for producing the same.
With the recent trend toward finer semiconductor devices, the area of information storage capacitor component has become smaller and smaller and the absolute value of capacitance has also become smaller and smaller. In case of a parallel flat plate electrode structure, a capacitance C can be defined by the following equation:
C=xcex5xc2x7S/d
where xcex5 is a permittivity of dielectric, S an area of electrode and d a film thickness (interelectrode distance) of dielectric. To secure a capacitance without increasing the area S of electrode used in the information storage capacitor component, it is necessary to use a dielectric material with a high permittivity xcex5 or make the film thickness d of dielectric smaller. The thickness of a thin oxide film is now made as small as about 10 nm, and in case of memory of high integration level of 64 M bits or more, an effort to make capacitor dielectric films thinner is almost reaching the limits, and thus development of capacitor insulation film materials with a higher dielectric constant xcex5 is in progress, and use of tantalum oxide or barium strontium titanate (BaxSryTisOt: BST) or the like is now investigated. As in case of tantalum oxide or barium strontium titanate, the dielectric constant is called xe2x80x9ca high dielectric constantxe2x80x9d, if a dielectric constant is 5 or more. Furthermore, use of a ferroelectric such as lead titanate zirconate (PbxZryTisOt: PZT), etc. is also now investigated for the nonvolatile memory.
It is known that oxides such as tantalum oxide, BST, PZT, etc. fail to show better characteristics, if not heat treated, and thus it is necessary to conduct heat treatment at about 600xc2x0 C. or higher, preferably at about 700xc2x0 C. or higher after the formation of an oxide film. For metallic wiring susceptible to the heat treatment, e.g. tungsten, as disclosed in JP-A-10-116905, is used as a high melting point metal.
However, when the aforementioned prior art was applied to semiconductor devices such as 256 M bit DRAM or system LSI (semiconductor device with memory LSI and logic LSI mounted together on a single chip), such problems as breaking of tungsten interconnects, lowering of semiconductor device reliability, lowering of yield, etc. were encountered in some cases.
The present invention has been established to dissolve at least one of the aforementioned problems.
The present invention provides a semiconductor device, which comprises a semiconductor substrate; a metal interconnect composed of tungsten as the main constituent material and containing molybdenum, formed on one principal side of the semiconductor substrate; and a capacitor component comprising a first electrode formed on the one principal side of the semiconductor substrate, an oxide film with a high dielectric constant or ferroelectricity formed in contact with the first electrode, and a second electrode formed in contact with the oxide film.
The present invention further provides a process for producing a semiconductor device, which comprises a step of providing a semiconductor substrate; a step of forming a metal interconnect, composed of tungsten as the main constituent material and containing molybdenum on one principal side of the semiconductor substrate; a step of forming a first electrode on the one principal side of the semiconductor substrate; a step of forming an oxide film with a high dielectric constant or ferroelectricity so as to be in contact with the first electrode and then heating the oxide at a temperature of 600xc2x0 C. or higher; and a step of forming a second electrode in contact with the oxide film.